With the advent of forced air heating and cooling in homes, commmercial buildings, manufacturing plants and the like, the use of air filters has become widespread. Initially the air filter assemblies were difficult and costly to manufacture and frequently were awkward to handle. The frames utilized to accommodate the filter panels or pads were of costly construction because of the need for numerous components requiring an inordinate amount of manual labor to assemble. Frame constructions were subsequently improved by significantly reducing the number of components and the amount of manual labor required. Such improved frame constructions, however, were not without shortcomings, e.g., they did not provide adequate support for the pliable filter panel normally employed in such an assembly. Where inadequate support was provided for the filter panel, the latter became severely distorted when subjected to the flow of air therethrough whereby in certain instances peripheral portions of the filter panel became disengaged from the frame and thus, provided gaps through which the air could flow unfiltered.
In other instances, the prior frame constructions were susceptible to being torn or permanently deformed when the latter was subjected to normal handling during shipping, storage, or when being installed in a heating and/or air conditioning unit.